FIG. 1 illustrates a typical arrangement for charging an electric vehicle (EV) such as a plug-in electric vehicle (PEV), plug-in hybrid electric vehicle (PHEV), etc. Electric vehicle supply equipment (EVSE) 10 receives electric power from a utility grid or other source and transfers it to the vehicle 12 through a cord 14 and connector 16 that plugs into a mating inlet 18 on the vehicle. In this example, the AC power from the grid is converted to DC power by an on-board charger 20 in the vehicle to charge the battery 22.
The EVSE, which is also referred to as supply equipment, a vehicle charger, a charging station, a charger, etc., may be realized in several different mechanical configurations. EVSE are frequently installed as wall-mounted units in garages and on buildings where vehicles can be parked inside or close to the building. In outdoor locations, especially parking lots and curbsides, EVSE are commonly installed on pedestals. EVSE may also take the form of a cord set which is sometimes referred to as a travel charger, portable charger, handheld charger, etc.
The connector 16 and inlet 18 typically utilize a conductive connection in which the electrical conductors in one connector make physical contact with the electrical conductors in the other connector. Other systems utilize inductive coupling in which energy is transferred through magnetic coils that are electrically insulated from each other.
To promote interoperability of vehicles and supply equipment, the Society of Automotive Engineers (SAE) has developed various standards that define mechanical configurations of connectors for charging vehicles, as well as the arrangement and function of electrical contacts within the connectors. One standard known as SAE J1772 is of particular interest because virtually every automaker in the U.S., Japan and Europe has announced plans to use J1772 compatible connectors for models sold in the U.S. This standard relates to conductive charging systems and covers both AC and DC connections.
FIG. 2 illustrates a reference design for a conductive vehicle charging system under the J1772 standard. A vehicle 30 is coupled to EVSE 28 through a coupling inlet 26 on the vehicle and coupling connector 24, which is typically connected to the EVSE through a flexible cord. AC power is transferred to the vehicle through terminals 1 and 2 of the coupling. A charging circuit interrupting device (CCID) 44 interrupts the flow of AC power if the difference between the current flowing in the two AC conductors exceeds a predetermined threshold, which typically indicates a potential ground fault condition. An on-board charger 32 in the vehicle converts the AC power to DC current for charging the battery 34.
Terminal 5 of the coupling connects safety grounding conductors in the EVSE and the vehicle. A control pilot signal is connected through terminal 6 and enables basic two-way communications between the EVSE and the vehicle. For example, the control pilot enables a charge controller 36 in the vehicle to determine the maximum amount of AC current available from the EVSE, while it enables the EVSE to determine if the vehicle requires ventilation for charging and if the vehicle is ready to receive power. The return path for the control pilot signal is through the grounding path which enables it to serve a safety function: if the safety pilot signal is not present, control electronics 42 in the EVSE assumes the ground path has been compromised and causes the CCID to interrupt the flow of AC power to the vehicle.
A proximity device 40 enables the vehicle to verify that it is mechanically connected to an EVSE system. The implementation details of proximity detection are left to the discretion of the manufacturer, but the J1772 standard identifies the use of magnetic proximity detectors as an acceptable technique. For AC charging, only terminals 1, 2, 5, and 6 are required. DC charging requires the use of optional terminals 3 and 4, as well as the establishment of a more sophisticated communication link through optional terminals 7-9 which are not illustrated.
The J1772 standard defines different types of charging including AC Level 1, which utilizes the most common 120 Volt, 15 Amp grounded receptacle, and AC Level 2, which utilizes a dedicated AC power connection at 208-240 Volts nominal and 32 Amps maximum. DC charging is defined as a method that utilized dedicated direct current (DC) supply equipment.